Reaction of hydrocarbons



Patented Dee 21, 1943 ENT osrica 2,337,265 1 REACTION or maocaaeousEugene H. OakleynEl Cerrito, and Laverne P. Elliott, Berkeley, Calif.,assignors to Standard Oil Company of California, San Francisco, Calif.,a corporation of Delaware v Application December 16, 1940, Serial No.310,332 5 Claims. (Cl. 260-683.4)

This invention relates to an improved process for the alkylation ofisoparaifins and, more par-- ticularly, to a process wherein, saidisoparaifins are .alkylated by means of an alkylated acid for theproduction of isoparaifins suitable for use in liquid motor fuels ofhigh antiknock value and for other uses.

It has previously been disclosed that the isoparaffinic hydrocarbons,such as isobutane and isopentane, may be caused to react with theolefins of low molecular weight, such as propylene,

the butenes and the pentenes, by means of liquid acid catalysts, such asconcentrated sulfuric acid.

- The products of this reaction correspond insubfor use in thepreparation .of aviation motor fuels.

In one method which has been proposed for effecting the foregoingalkylation reaction, the

isoparaffin and olefin reactants are intimately contacted in thepresence of the liquid sulfuric acid catalyst and the alkymers formedare separated from the catalyst and unreacted raw material by anyappropriate means.

In another specific method advantage is taken of the discovery that thealkylation of an isoparaflin by an olefin, in the presence of a strongalkylation of an isoparaflin by an olefin in two separate stages inwhich the conditions of reaction may be independently controlled.

It is another specific object of the present invention to provide animproved process for utilizing hydrocarbon mixtures comprising olefins,isoparafilns and normal paraflins-for producing alkymers of the olefinswith the isoparaffins by eifecting the reaction in two separate stagesthrough the agency of an acid alkylating medium.

It is a still more specific object of our invention to provide, in amethod of producing alkymers from a mixture of isoparafilns and olefinsby a two-stage reaction, an improved process wherein the alkylation ofthe isoparafiin is substantially confined to the second stage in whichconditions most favorable to said alkylation may be maintained. r

It is another specific object of the present invention to provide animproved two-stage process for alkylating isoparaflins with olefins.wherein the acid is alkylated in the first stage by means of olefins ingas phase, a liquid hydrocarbon layer is separated from the acid andalkylated acid is used to alkylateliquid isoparamn in the second stage.

Other important objects of the invention will I be apparent from thefollowing description and acid of the nature of sulfuric acid, is not asingle reaction but is in fact the sum of two entirely distinctreactions which may therefore be separated and each effected under theconditions best suited to it with considerable improvement in operationand in the net result obtained.

The maximum benefits to be derived from the above method of conductingthe alkylation reaction in two separate stages are, however, largelydependent upon the specific manner in which each stage is effected andthe arrangement of the stages with respect to other necessary operationsin a complete process for producing alkymers boiling in the rangeofmotor fuels from readilyavailable raw materials.

It is an object of the present invention to provide an improved processfor effecting the alkylation of an isoparafiin wherein improved yieldsof alkymer of improved quality are obtained.

It isa more specific object of this invention .to provide an improvedprocess for effecting the the appended claims.

The two entirely separate and distinct reactions mentioned above asresulting in the alkylation of an isoparaffln by an olefin in thepresence of -a strong acid of the sulfuric acid type are; first, thealkylation of the acid by the olefin to form a solution containing someof the alkyl acid ester of the acid, some polymers and apparently someas yet unidentified compound between the acid and the olefin or apolymer or other reaction productthereof, and second, the reaction ofthe alkylated acid solution thus produced with the isoparaifin to formthe alkyl isoparafiin or alkymer and release the acid.

In the alkylation of isobutane with butene by means of sulfuric acid,the acid alkylation reaction takes place readily with acid of anystrength above about 50% H2304 at ordinary atmospheric temperatureswiththe butene in and theisobutane alkylation reacizionsJI-r maximumbenefits are, of course, not obtained.

Convenient sources of olefins and isoparamns in large volume fortheproduction of" alkymers of high antiknock value boiling in the range ofaviation motor fuels are to be found in the mixtures of C5 and lighterhydrocarbons produced during the cracking of petroleum oils or by thepartial dehydrogenation of natural gasfractions. In such mixturesolefins, isoparaifins and normal parafflns usually occur together inproportions determined by the severity of the cracking ordehydrogenation treatment and the specific nature of the oil or naturalgas fraction treated. In applying the above two stage method ofalkylation to such a mixture it is most convenient to effect the acidalkylation step by contacting the whole mixture withthe acid under theappropriate conditions whereby the olefin is readily taken up by theacid, leaving the mixture of normal and isoparafiins. Unless, however,special precautions are taken t prevent it ot completely separated thecording to the continuous countercurrent principle wherein the gaseoushydrocarbon mixture containing both olefin and isoparafiln is .caused topass upwardly through a vessel of appropriate dimensions, such as a x40'cy'lindrical drum, while the liquid acid is dispersed from a suitabledistributor placed near the top of said vessel and fiows by gravity oversuitable trays or an appropriate packing disposed therein to provide a.large surface of contact "between. the

' descending acid and the 1 ascending ydrocarbon gases. The acid may becollec' a reservoir at the bottom of the vessel and provision maybe madefor the entering hydrocarbon gases to bubble therethrough. Theparaifinic gases substantially free of olefins are collected at the topof the acid alkylation vessel and appropriately disposed of, asdescribed hereinafter, while the alkylated acid is withdrawn from thebottom of the vessel and sent to the hydrocarbon alkylation stage.

In any such method of operation the relation between the quantities ofhydrocarbon and acid charged per unit of time may be varied so as toremove substantially all of the olefin without ef fecting an intimacy ortime of contact'that will result in an undesirable amount of alkylationof some alkylation of the isoparafiin will be effected at the same time,even though the conditions are not particularly favorable to it, and, aspointed out above, the maximum possible benefits of the two-stage methodwill accordingly not be realized.

We have now found that by effecting the acid alkylation stage in aparticular manner the advantage of employing a hydrocarbon mixturecontaining both .olefins and isoparafiins for alkylating the acid in thefirst or acid alkylation stage of a two-stage isoparafiin alkylationprocess may be enjoyed without effecting an undesirable amount ofisoparaflin alkylation in the said first stage, and a considerableimprovement in the over-all operation of the process and in the quantityof the alkymer product produced may be effected.

According to one embodiment of the process of the present invention, theacid alkylation reaction isefiectedby dispersing the acid in andpermitting it to fall by gravity through a body of ascending hydrocarbongas mixture containing both olefin and isoparaflin and separating theaccumulated acid containing the alkyl acid eter and other compoundsformed during the acid alkylation reaction without efiecting sub--stantial or prolonged contact between the acid and the hydrocarbonsufiicient to give the intimacy of contactwhich is necessary to effectsubstantial alkylation of the isoparafiin.

According to another specific embodiment of the process of the presentinvention, the hydrocarbon gas mixture containing olefins andisoparafiins may be bubbled into and caused to ascend through a columnof the liquid acid whereby the olefin is taken up by the acid andthe'isoparaflin is separated and removed from the top of the column. v

According to still another and preferred embodiment of the process ofthe present invention, the acid alkylation reaction is effected actheisoparaflin under the temperature and other conditions most suitable tothe acid alkylation reaction and which may be relatively unsuitable tothe isoparafiin alkylation reaction.

A considerable portion of the acid entering the acid alkylation zonewill ordinarily be acid which is recycled from the hydrocarbonalkylation zone. Such acid will usually be found to carry a considerableamount of hydrocarbon containing alkymer product from the hydrocarbonalkylation zone. It is' a particular feature of the present inventionthat provision is made in the acid alkylation zone for collecting thishydrocarbon separately from the normal and isoparaffins charged theretoalong with the olefin used to alkylate the acid, as will be more fully.explained hereinafter.

A convenient widely available source of isoparafllnfor alkylation, andof olefin-for effecting the alkylation, is the C4 or butene-butanefraction of the hydrocarbons resulting from the cracking of petroleumfor the production of motor gasoline. The analysis of a typicalbutene-butane cut produced in the liquid phase cracking of a petroleumoil is as follows:

According to the process of the present invention, such a fraction asproduced, or after appropriate purification for the removal of nitrogenand sulfur-containing compounds or after selective polymerization forremoval of the isobutene or the isobutene and a portion of the normalbutenes, is contacted as just described with a strong acid of thesulfuric acid type,-such as concentrated sulfuric acid,'whereby thebutenes are caused to react with the acid forming the correspondingbutyl acid esters and other compounds mentioned above. The remaining,substantially olefln free, mixture of normal and isobutane isiractionally distilled to separate the two and the isobutane so producedis then very intimately contacted with the alkylated acid solutionwhereby the isobutane is alkylated to .produce a mixture of hydrocarbonshaving high antiknock value and boiling substantially in the range ofaviation gasoline.

The process of our present invention may be betterunderstood byreierring to the figure of the attached drawing. A hydrocarbon mixturecontaining olefins and both normal and isoparaffins, such as the abovebutane-butene cut, produced in a petroleum cracking process or by thepartial dehydrogenation of a fraction from natural gas, with or withoutfirst having been treated for the removal of nitrogen andsulfur-containing compounds may be passed through line 6! to apolymerization plant 62 wherein the isobutene or the isobutene and aportion of the normal butene is polymerized by any known method and theremaining mixture, still containing some normal butene, is led in gasphase through line I and valve 2 and injected through an appropriatemanifold IOI into the acid alkylating zone 3 wherein it is contactedwith sulfuric acid containing between about 50 and 100% H2804 in-'troduced from line 5 through an element t, which is preferably a devicefor distributing the sulfuric acid uniformly over the trays, Raschigrings or other means provided for exposing a large surface of acid tothe ascending hydrocarbon gas mixture. If the conversion of a portion ofthe butene to polymers is not desired, the whole C4 cut may be chargedthrough lines 63 and I direct to the acid alkylating zone 3. It has beenfound that by conducting the acid alkylating reaction in the gaseousphase it -'is possible to collect in liquid phase thehydrocarbons whichenter the acid alkylating zone 3 with the recycled acid, thus keepingthem separate from the saturated hydrocarbon gases associated with theolefin in the raw material charged to zone 3. The recovery of alkymerproduct contained in the recycled hydrocarbon liquid is therebymaterially simplified while its quality is preserved through preventingits deterioration by the acid. The liquid hydrocarbon layer, 317, whichis collected in zone 3 maybe discharged through valve it into line 12and forced by pump H through an appropriate cooler and condenser it toline 26 and thence to the alkymer stabilizer 2s.

The temperature in the acid alkylating zone t should be maintainedabove'the melting point of the alkylated acid solution but below thepoint at which substantial destructive reaction between the acid and thebutene takes place. A convenient range of temperature has been found tobe from about to 150 F. with the preferred temperature being toward thelower side of this range in order. to minimize possible undesirable sidereactions, which not only consume valuable butene but also causedeterioration of the acid as an alkylation medium. The rate at whichhydrocarbon and acid are supplied to zone 3 may be so regulated as togive any desired concentration of butyl acid sulfate and other productsof the acid alkylation reaction in the separated acid layer, indicatedby So. Consistent with the conditions prevailing in the acid alkylatingzone I and the greatest advantage with respect to effecting succeedingstages of the process, the concentration of the total reaction productsin solution in the alkylated sulfuric acid leaving the acid alkylatingzone 8 may be from a fraction 013- 1% to about 20% byweight for the bestresults,

, depending upon the particular combination or conditions employed, thepreferred concentration usually, however, beingtoward the low side ofthis range.

The mixture of normal and isobutane remaining after absorption of thebutenes is passed through line 6, compressor I06 and condenser H8 to abutane still 1, equipped with an appropriate heating device 55, whereinseparation of the isobutane from the normal butane is effected, thelatter being removed from the system through line H and valve ii. Thesubstantially pure isobutane passing overhead from still i is conduct-.ed through line 8 and condenser 9 to receiver it from which propane orother uncondensed gas may be vented through valve t8. A portion of theliquid isobutane collected in receiver it may be returned through valveit and line 15 to provide reflux liquid in the butane still while theremainder is led through valve i3 into manifold It for mixture with thealkylated acid solution whichis conducted from zone 3 through valve 18,line it, pump lit and cooler 64 for removing exothermic heat of reactionwhen desired.

The mixture of isobutane and alkylated acid solution in manifold is isled directly into an appropriate device I! for efiecting intimat contactbetween an aqueous and an oil phase. In order to insure the completionof the alkylation reaction, the mixture may be passed from contactor I?through an appropriate auxiliary device 2! wherein additional turbulenceand time for reaction may be DI'OVld'Edr The temperature in thehydrocarbon alkylatlon zone (I1, 20 and 2|) should be under accuratecontrol, and to this end a coil 20 may be interposed for adding orremov- I ing heat as desired. From the auxiliary contactor ii themixture of acid, unreacted isobutane and alkymer product is passedthrough line 22 into an acid separator 23 wherein acid is collected asindicated at 23a for removal from the system through line B0 and valvet2 or for return through valve ii, line 6t, pump 66 and valve 69 to line5 and the acid alkylating zone 3 or through valve 68 to line l9 and thehydrocarbon alkylating zone li-Zi.

The hydrocarbon phase comprising isobutane and alkymer product isremoved from separator 23 through valved line 26 and passed throughvalve and line 2% to an alkymer stabilizer 29 or, if desired, a portionof the hydrocarbon phase may be returned through valve 27 and line 28 tothe manifold It, as more fully described hereinafter.

In the alkymer stabilizer 29 separation is effected between the alkymerproduct and-the excess of isobutane which is then led through line '3tand condenser 3! to receiving drum '32 while the alkymer product ispassed through line 33 and valve 34 to an alkymer distillation unit 35.A portion of the liquid isobutane collectedin receiver 32 may bereturned through valve 31 and line 38 to provide reflux liquid to thealkymer stabilizer 29 while anotherportion' of the liquid isobutane ispassed through valveand line to manifold I6. 1 I

In order that the hydrocarbon alkylating reaction in zone !'l-2l may beas rapid and complete as possible, itis desirable to provide a highratio of isoparaflin to total alkyl components. in

the alkylated acid solution, for instance, of the order of ten to one orabove by weight. In order to produce the highest possible yield ofalkymers having the highest antiknock value, it has been found desirableto maintain this ratio in a somewhat higher range as, for instance.between about 100 and 700 to 1. In order that such ratio may beestablished and maintained, it is neces-' sary that the hydrocarbonmixture entering zone 3 from line I contain more isoparaflin thanolefinor that additional isobutane be supplied to the system from an externalsource through valve 39 and line 39. When additional isobutane is notreadily available or for other reasons it is desired to employ only thebutene and isobutane of the C4 cut for alk'ylation, the desired ratiomay be established by first polymerizing 'the excess butene as aboveindicated. An additional advantage is obtained by so operating suchpolymerization step that the isobuten is selectively polymerized sincenot only does di-isobutene when hydrogenated give a product having ahigher octane number than the hydrogenated normal or mixed butenepolymers but the alkymers of isobutane with normal butene have a higheroctane number than those produced from isobutane with isobutane. Theratio of isoparaifin to acid alkyl- I ation products may also beaugmented by recirculating a portion of the hydrocarbon phase fromseparator 23 to manifold 16, as above-mentioned. Since the hydrocarbonliquid collected at 3b 1 will ordinarily contain traces of normalbutane, it

will usually be desirable to permit this to remain in the alkymerproduct leaving stabilizer 29. This product is led through line 33 andvalve 34 to still 35, which contains an appropriate heating element 51,for fractionation to produce a motor fuel of the desired end point whichpasses through line 45 and condenser 46 to receiving drum 4'! from whicha portion of the condensed alkymers may b returned through valve 48 andline 49 to provide reflux liquid in the still 35 and from which alkymersmay be removed to storage through valve 50. Thehigher boiling alkymers,which constitute the bottoms from alkymer still I I, may be removed fromthe system through linev 6i and valve 52, though it has been found thatif they are returned through-valve 53 and line 54 to manifold l6 and thehydrocarbon alkylation zone li -2|, the. further production of heavyalkymers may be substantially repressed and a maants 10st to sidereactions is materially reduced by efiectingthe alkylation reaction intwo stages, as above described, and carefully controlling the reactionconditions in each stage, a small quantity'of highly unsaturatedterpene-like hydrocarbon still accumulates in the acid and eventuallyinterferes with its further use as the alkylation medium. It has,however, been found that if a small portion of the acid in the system iscontinually replaced with fresh acid,'the activityof the'acid in thesystem may be indefinitely pro- Y longed. Acid for charging the systemoriginally .and for such replacement 'may be supplied through pump 44and valve 43 'to line I and the J acid 'alkylating zone I or, ifpreferred, the replacement acid may be addedtothe alkylated acidentering the-hydrocarbon alkylation zone "-4! through a connectionnot'shown. Acid to compensate for the fresh acid added may be removedfrom line 40 through valve 42.

One particular feature of the process of the butane still 1 between theacid alkylation zone a and the hydrocarbon alkylation zone "-21. By

eliminating the normal butane from the mixture of hydrocarbons in thesystem atthis point, after removal of olefins in the acid alkylationzone 3 but prior to the hydrocarbon alkylation zone, a

considerable saving in distillation is effected over that which would benecessary if the normal butane removal were effected at a point in thesystem, beyond the manifold IS, in which the isoparaifin ratio ismaintained at a high value by isobutane recirculation, and/or additionas above described. Another essential feature of the process of thepresent invention consists in maintain- I 5 ing the hydrocarbonmixturecontaining the olefins with which the acid is alkyiated in the vaporphase and thereby making possible the separation of a hydrocarbon liquidphase containing alkymer product from the acid which is recycled fromthe hydrocarbon alkylation zone.

Operation of the process of the present invention, as above described,may be better understood by reference to the following example: Abutene-butane cut containing 2.0% propylene,

55 11.1% propane, 17.0% normal butenes, 18.3% isobutane and 50.5% ofnormal butane was charged in gas phase to the acid alkylating zone 3while strong sulfuric acid containing a substantial proportion of acidrecycled from the hydrocarbon alkylation zone was charged at a ratesufficient to absorb the olefin contained, in the gas. The temperaturein the acid alkylation zone was maintained between 50 and 60 F. and thepressure was about atmospheric. A liquid hydrocarbon phase wascollected, as previously described, which contained over 10% of thetotal alkymer product. i

I The alkylated acid solution thus produced in zone 3 was thenintimately contacted with a bydrocarbon mixture containing 84.8%isobutane,

8% normal butane and 7. 2% propane in the hydrocarbon allq'lation zone(i6, i1, 20 and 2|) at a temperature of to F. and a pressure of about150 pounds per square inch. The vol- 5 ume ratio of hydrocarbon to acidwas 2.3 to 11.5. After separation in zone 23 and stabilization instabilizer 29, the alkymer product, amounting to I able isoparafiins, itis not limited to such raw I materials and. may be employed when theolefins and isoparafiins are introduced separately 50 from totallydifferent sources.

Among the significant features or the proces of the present invention,which may be reemphasized in summary, are the alkylation of an acid ofthe sulfuric acid type by a gaseous hydrocarbon mixture containingolefin and isoparafiin whereby the olefin is caused to alkylate the acidbut not the isoparafiin, the alkylation of the iloparafiln in a separatezone in liquid phase by the alkylated acid in the entire absence of anyadditional olefin, the return of heavy alkymers from the alkymer stillto the hydrocarbon alkylation zone, the return of acid liberated in thehydrocarbon .alkylation zone to the acid alkylationz'one, the separationand colpresent invention resides in the position of the lection in theacid-alkylation zone of a liquid hydrocarbon phase containing allwmerproduct and the removal of normal butane from the system at a pointprior to the hydrocarbon alkylation stage in which it is desirable tomaintain a high proportion of isobutane.

While the process of the present invention has been explained withparticular reference to the alb'lation of isobutane by butene, usingsul- I our improved process for efiecting the alkylation of an isoparamnin two entirely'separate stag'es, we claim as our invention:

1. Process of alkylating an isoparafiln for the production of isoparamnsof higher molecular weight, which comprises: bringing an acid alkylationcatalyst recycled from a second zone and containing alkymer product intocontact with a gaseous mixture containing normal paraffin, isoparamn andolefin in a first zone, under conditions regulated to favor theformation of alkyl acid ester and to suppress isoparamn alkylation andother possible reactions, thereby form-' fractionally separating normalfrom isoparamns ing a solution of alkyl acid ester in an excess of theacid and liberating asan acid-inso ubl liquid phase the alkymer productcontained in the recycled acid, removing the said liberated liquidalkymer product from the first zone, removing unreacted gaseous normaland isoparaffins from the said first zone, fractlonally separatingnormal from isoparaffins in the gaseous mixture removed from the saidfirstzone and passing the separated isoparafiins to a second zone,alkylating the said isoparafiin in liquid phase by intimately contactingit in thesecond zone with the solution of alkyl acid ester formed in thefirst zone, under conditions favorable to said a1- kylation, whereby anisoparafiinof higher molecular weight is produced and acid alkylationcatalyst is liberated, effectinga substantial separa paraffin to asecond zone, alkylating the said isoparaifin in liquid phase byintimately contacting it in the second zone with the solution of alkylacid ester formed in the first zone, under conditions favorable to saidalkylation,;whereby an isoparamn of higher molecular weight is producedand acid alkylation catalyst is liberated, effecting a substantialseparation of hydrocarbons from said liberated acid alkylation catalyst,and recycling at least a portion of said liberated acid alkylationcatalyst to the aforesaid first zone for re-alkylation.

3. Process of alkylating an isoparamn for the production of isoparamnsof higher molecular weight, which comprises: bringing an acid alkylationcatalyst recycled from a second zone and containing alkymer product intocontactwith a gaseous mixture containing normal par, isopar and olefinin a first zone, under condi- I tions regulated to favor the formationof allryl acid ester and to suppress isoparaffin alkylation and otherpossible reactions, thereby forming a solution of alkyl acid ester in anexcess ofthe acid and liberating as an acid-insoluble liquid phasethe-slimmer product contained in the recycled acid, removing the saidliberated liquid alkymer product from the first zone and passing it toan alkymer stabilizer in order to recover stable allrymers therefrom,removing unreacted gaseous normal and isoparafiins from the said firstzone,

in the gaseous mixture removed from the said first zone and passing theseparated isoparaflin to a second zone, alkylating the said isoparafiinin liquid phase by intimately contacting it in the second zone with thesolution of alkyl acid ester formed in the first zone, under conditionsfavorable to said alkylation, whereby an isoparamn of'higher molecularweight is produced and acid alkylation catalyst is liberated, effectinga substantial separation of hydrocarbons from said liberated acidalhylation' catalyst and passing the separated hydrocarbons to analkymer stabilizer in order togrecover stable alkymers therefrom, andrecycling at least a portion of said liberated acid aikylationcatalystto the aforesaid first tion of hydrocarbons from said liberated acid.

alkylation catalyst, and recycling at least a portion of said liberatedacid alkylation catalyst to the aforesaid first zone for re-alkylation.

2. Process of alkylatlng an isoparafiin for the production of isoparamnsof higher molecular weight, which comprises: bringing an acid alkylationcatalyst recycled from a second zone and containing allrymer productinto contact with a gaseous mixture containing normal parafiln,isoparafiln and olefin in a first zone, under conditions regulated tofavor the formation of alkyl acid ester and to suppress isoparamnalkylation and other possible reactions, thereby forming a solution ofalkyl acid ester in an excess of the acid and liberating as anacid-insoluble liquid phase the alkymer product contained in therecycled acid, removing the said liberated liquid allwmer product fromthe first zone and passing it to an alky er stabilizer in order torecover stable alkymers therefrom, removing unreacted gaseous normal andisoparaffins from, the said first zone, fractionally separating normalfrom isoparafiins in the gaseous mixture removed from the said firstzone and passing the separated imzone for re-alkylation.

4. Process of alwlating isobutane for the production of isoparamns ofhigher molecular weight, which comprises: bringing an acid alhyl-= ationcatalyst recycled from a second zone and containing alkymer product intocontact with a gaseous mixture containing normal butane, isobutane andbutane in a first zone, under conditions regulated to favor theformation of butyl acid ester and to suppress isobutane alkylation andother possible reactions, thereby forming a solution of butyl acid esterin an excess of the acid and liberatingas an acid-insoluble liquid phasethe .alkvmer product contained in therecycled acid, removing the'saidliberated liquid. 'alkymer product from the first zone, removingunre'acted gaseous normal and isobutanes from the said first zone,fractionally separating normal butane from isobutane in the gaseousmixture removed from the said first zone and passing the separatedisobutane to a second zone, alkylating the said isobutane in liquidphase by intimately contacting it in the second zone with the solutionof butyl acidester formed in the first zone, under conditions favorableto said alkylation, whereby an isoparaifin of higher molecular weight isproduced and acid alkylation catalyst is liberated, effecting asubstantial separation of hydrocarbons from said'liberated acid mic-ction catalyst, and recycling at least a portion of said liberated acidalkylation catalyst to the aforesaid first zone for re-alkylation. v

5. Process of alkylating isobutane for the production of isoparafllns ofhigher molecular weight, which comprises: bringing a sulfuric acidalkylation catalyst recycled from a, second zone and containing aikymerproduct into contact with a gaseous mixture containing normal butane.isobutane and butene in a first zone, under conditions regulated tofavor the formation of butyl acid sulfate and to suppress lsobutanealkylation and other possible reactions, thereby forming a solution ofbutyl acid sulfate in an excess of sulfuric acid of alkylating strengthand libcrating as an acid-insoluble liquid phase the alkymer productcontained in the recycled acid, removing the said liberated liquidalkymer prodous normal and isobutanes from the said first zone,fractionally separating normal butane from isobutane in the gaseousmixture removed from the said first zone and passing the separatedisonot from the'flrst zone, removing unreacted gasebutane to a secondzone, alkylating the said isobutane in liquid phase by intimatelycontacting it in the second zone with the solution of butyl acid sulfateformed in the first zone, under con- EUGENE H. OAKLEY. LAVERNE P.EILIOTI'.

